It is now well established that variations in early sensory experience can produce changes in neuronal organization. The functional significance of these neurological alterations, however, remains unclear. The present proposal is directed toward study of early environmental influences on the development of brain morphology and behavior. It is concerned most directly with perceptual capacities, specifically with how visual pattern perception is affected by postnatal visual deprivation and how such environmental influences on behavior are mediated by morphological change, as revealed by the Golgi technique.